Problem: If $a + b + c = -9$ and $x + y + z = 10$, what is $-3x - 3y - 3z + 5c + 5b + 5a$ ?
$= 5a + 5b + 5c - 3x - 3y - 3z$ $= (5) \cdot (a + b + c) + (-3) \cdot (x + y + z)$ $= (5) \cdot (-9) + (-3) \cdot (10)$ $= -45 - 30$ $= -75$